The present invention relates to dispensing mechanisms and, more particularly, to a sand dispensing mechanism wherein sand from two different storage bins can be loaded into and discharged from two sets of dispensing tubes.
As described in U.S. Pat. No. 3,735,796, assigned to the assignee of the present invention, it is known in the metal casting art that molds must be provided with risers. Such risers assure that gases can exit the mold during pouring, especially in the bottom pressure casting of railway wheels using two piece graphite molds that are sealed together during pouring. Further, the risers assure that sufficient metal is present in the mold during cooling to flow back down into the mold cavity to minimize casting shrinkage or the formation of cavities.
In graphite molds, it is desirable to line such risers with a refractory sand-resin binder mixture to protect the mold. The bottom sand in such riser is desire to be fine as such sand will face the casting. It is desirable if such sand is new, unbaked sand. The sides of the riser can be lined with coarser sand, which could be reused from prior riser lining. The lined riser has been previously heated, so an amount of the lining sand will harden and remain, while a portion of the sand will be shaken out for reuse. The metal mold liner that formed the bottom of the riser for the sand to form about is removed. A hole is punched in a raised portion of the facing sand to form a sprue having a smaller cross section than the riser to facilitate knocking off the riser after pouring and solidification of the casting. The sprue opening permits gas outlet and metal storage in the riser.
It is an object of the present invention to provide a sand dispensing mechanism capable of readily depositing one type of sand in the bottom of the riser openings and another type of sand to line the riser sides.